The following U.S. Patents are incorporated herein by reference.
U.S. Pat. No. 8,668,538 discloses a marine engine having an exhaust system comprising a cylinder block having first and second banks of cylinders that are disposed along a longitudinal axis and that extend transversely with respect to each other in a V-shape so as to define a valley there between. A catalyst receptacle is disposed in the valley and contains at least one catalyst that treats exhaust gas from the marine engine. An exhaust manifold conveys exhaust gas from the marine engine to the catalyst receptacle. The exhaust manifold has a first port receiving exhaust gas from the first bank of cylinders, a second port receiving exhaust gas from the second bank of cylinders, and a conduit conveying the exhaust gas from the first and second ports to the catalyst receptacle. From the first and second ports to the catalyst receptacle, the conduit only reverses direction once with respect to the longitudinal axis.
U.S. Pat. Nos. 8,444,447 and 8,298,026 disclose an outboard motor including an engine, an exhaust guide, and a catalyst. The engine includes a cylinder and crankshaft. The crankshaft is disposed along a vertical direction. The exhaust guide is arranged to support the engine from below. The catalyst is disposed in an interior of the engine. The engine includes a cylinder body. The cylinder body includes a housing portion arranged to house the catalyst. The cylinder body includes a first exhaust passage that includes an interior of the housing portion. The catalyst is inserted into the housing portion from below and is sandwiched from above and below by the housing portion and the exhaust guide.
U.S. Pat. No. 7,954,314 discloses an engine provided with a cavity so that a catalyst member can be contained within the engine when an engine head portion is attached to an engine block portion. This attachment of the engine head portion and engine block portion, which forms the engine structure, captivates the catalyst member within the cavity without the need for additional brackets and housing structures. The cavity is preferably located above or at the upper regions of first and second exhaust conduits which direct exhaust upwardly from the engine head portion toward the cavity and downwardly from the cavity within the engine block portion. The first and second exhaust conduits are preferably formed as integral structures within the engine head portion and engine block portion.
U.S. Pat. No. 5,916,132 discloses an engine exhaust emission control system in an outboard engine. The exhaust emission control system has a catalyst unit mounted in an engine block exhaust gas passage in the outboard engine. The catalyst unit comprises a catalyst carrier having at least one catalyst element carried therein and a flexible porous bag having at least a portion of the catalyst therein. The catalyst unit is formed to be positioned within the engine block exhaust passage so as to extend there-along and the catalyst unit is removably inserted and detachably mounted in the exhaust gas passage.
U.S. Pat. No. 5,546,748 discloses a number of embodiments of exhaust systems for outboard motors including a combined catalyst bed and exhaust manifold forming member affixed within the cylinder block of the engine so as to be readily detachable for servicing. This combined member is provided with a separate cooling jacket for its cooling.